Minor fixes to steps and compliant poc control API

spec/test/features/control/insert/error_malformed.feature

@@ -20,6 +20,6 @@ Feature: Kapow! server reject insert requests with malformed JSON bodies.
         "id": "xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx"
       }
       """
-    Then I get bad request as response code
+    Then I get 400 as response code
       And I get "Malformed JSON" as response reason phrase
       And I get an empty response body